Period!!!

Okay... So about 4 or 5 years ago I had the implanon birth control out into my arm... Well a year and a half later I had it taken out to try for a family. My periods went back to "normal" ish... 2 years later here I am not and I decided to have it put back in.. I had the now nexplanon put in on April 22nd 2015... Well on May 5 I started my period and it lasted for 4 weeks on the dot. It stopped a week ago and now it came back. My question is is this normal?? I'm concerned BC this has never happened before but my ob/gyn said this is normal...

Should I be concerned or not??